Devices for engaging multiple items are employed in many different industries. In the packaging industry, a device that is part of a packaging system may be used to pick up items from a first location and deposit the items at a second location. For example, a plurality of items may be picked up from an item delivery lugged conveyor where the items are spaced at a first pitch, and then deposited into a container. In some packaging systems it may be necessary that at the second location, the items be spaced at a second pitch that is the same as the first pitch. In other systems, it may be necessary that at the second location, the items be spaced at a second pitch that is different from the first pitch.
It is often desired to retrieve and/or form the items obtained at the first location into separate groups of items such that each group has its items spaced at an item pitch. This item pitch is usually, but not always constant. Additionally each of the groups may be spaced apart from each other at a particular group pitch. The group pitch may be constant or variable between the groups (e.g. the spacing between a first group and a second group, may or may not be the same as the spacing between the second group and a third group. For example, the items may be deposited into receptacles that only accept a certain number of items. Thus, the items may have to be separated into groups for deposit into different receptacles, and it may be necessary to change the group pitch to accommodate the same.
During actual operation of a particular system in a particular “set-up”, in many situations it may not be necessary that the pitch between individual items in each group vary, but only that the pitch between the distinct groups be adjusted. However, it may be desirable to provide a system that can be relatively easily reconfigured, so that the system can also be operated to handle items that have a different item pitch spacing. Thus it is desirable to have a packaging system where the set-up of the item pitch can be readily modified.
It is known to employ a robot with a robot arm having an end effector mounted to its distal end. Such an end effector may have multiple pick up members, each pick up member having a mechanism, such as a suction cup, at its end for engaging an item. The pick up members may be arranged in a single line or may be arranged in an array of two or more lines. Moreover, it is often required that each pick up member be can be specifically positioned so that items may be accurately engaged and deposited in a particular manner.
Previous designs of end effectors capable of forming items into at least two groups include devices having single large cam slotted plates attached to the frame of the end effector. A cam follower was typically attached to each pick up member, and each follower was received in an individual slot in the slotted plate. Various grouping configurations were accomplished by varying the configuration of the slots in the plate.
However, there are drawbacks in having a single long cam plate with different cam slot angles. For example, to provide a given longitudinal arrangement of pick up members, pick up members at one location of a device may need to move longitudinally further than pick up members elsewhere. However, there will be a constraint in the angle of the slots (i.e. the slots can not be too shallow, otherwise the cam action will be difficult due to the forces being applied between the cam follower and the cam slot). To maintain a non-locking cam slot angle, the solution has been to make the cam plate relatively deep. However, this substantially increases the overall weight of the device. Additionally, having a relatively larger latitudinal travel distance, means that the cam followers may achieve a higher velocity when travelling in the slot and a significant shock force may be created when the cam follower is “bottoming out” or otherwise brought to a stop in the cam track.
It is also desirable, particularly in the packaging industry, to have devices which can be readily modified to enable them to be easily reconfigured to accommodate differences in an overall system set up. The set up required for the device in a particular system may have to take into account variations in one or more of: (a) the number of items to be picked up at the first station; (b) the pitch of the items at the first station; (c) the retrieval in, and/or the formation of, items into groups; (d) the configuration of the groups of items including the number of items in each group, the number of groups; and the spacing between the groups at the first location and at the second location. However, existing devices are not easily adapted to accommodate changes required to one or more of these parameters.
In view of the foregoing, improved devices for engaging and disengaging multiple items are desirable.